1. Field of the Invention
The present invention relates in general to a vehicle device which restrains vehicle passengers in the event of a vehicle collision, and more particularly, to an air-bag type passenger restraining device which includes an air-bag mounted on a holder and means which, upon a vehicle collision, moves the air-bag holder away from a seated passenger.
2. Description of the Prior Art
In order to clarify the task of the present invention, one vehicle device of the above-mentioned type will be outlined with reference to FIG. 17, which device was proposed by the same applicant through Japanese Patent Application No. 3-64166.
The device comprises generally an air-bag 101 installed in a steering wheel 103, a steering wheel retreating device 104 and a controller which controls operation of the air-bag 101 and the retreating device 104. Upon a vehicle collision, the controller functions so that the air-bag 101 is instantly inflated and at the same time the retreating device 104 retreats the steering wheel 103 by a given distance in a direction to increase a space between the steering wheel 103 and the passenger (viz., driver). The controller comprises an ignition switch 105, a judge circuit 107, a front sensor switch 109, a center sensor switch 111, a column switch 113, a battery 115 and a mercury switch 117. As shown, these parts constitute a first circuit which controls the air-bag 101 and a second circuit which controls the steering wheel retreating device 104.
When, due to a vehicle collision or the like, the front and center sensor switches 109 and 111 are actuated, the judge circuit 107 judges the collision and instantly ignites an inflater (not shown) of the air-bag 101. At the same time, the column switch 113 is actuated to energize the steering wheel retreating device 104 and thus the steering wheel 103 (more specifically, the steering column) is retreated by a given degree.
Because of enlargement of the space between the steering wheel 103 and the passenger upon the vehicle collision, the air-bag 101 can be inflated freely and easily within the space.
In the above-mentioned air-bag type restraining device, the retreat of the steering wheel 103 starts when the air-bag inflater is ignited. However, such retreat tends to induce a phenomenon wherein the practical passenger restraint by the inflated air-bag 101 is effected after the air-bag 101 has come to the retreated position. In this case, the passenger is forced to strongly bump against the air-bag 101. In fact, under such condition, it is difficult to provide the air-bag 101 with a so-called "passenger soft holding" irrespective of the enlargement of the space for the air-bag 101.
Furthermore, due to its inherent arrangement, the size (or stroke) of the air-bag 101 (more specifically, the thickness of the inflated air-bag) must be increased in accordance with the enlargement of the space. This will be understood from FIG. 18 which shows, by broken and solid lines, two positions of the inflated air-bag 101 on the steering wheel 103. The position shown by the broken line is the position which is taken by the inflated air-bag 101 just before the retreat of the steering wheel 103, while the position shown by the solid line is the position which is taken by the inflated air-bag 101 upon completion of the retreat. The stroke of the air-bag 101 is denoted by reference "LA" and the degree of the retreat of the steering wheel 103 is denoted by reference "LB". As is seen from the drawing, in order to provide the inflated air-bag 101 with "a sufficient passenger soft holding function", it is necessary to increase the thickness of the inflated air-bag 101 by a degree corresponding to the retreat "LB" of the steering wheel 103. This induces a bulky construction of the air-bag system.